In either of Japanese Patent Applications Nos. 59-120395 (published Jan. 7, 1986 under No. 61-1769) and 60-298461 (published July 16, 1987 under No. 62-160371) the inventor hereof has proposed a folding stage system of a type similar to the type of a folding stage system which will be proposed herein, that is, a stage system which includes guide posts fixed to a support wall structure and may be compactly folded to a vertical position immediately in front of the support wall structure and unfolded forward to provide a relatively large stage. The stage system proposed in the application No. 60-298461 has a central foldable link mechanism and foldable side link mechanisms which connect a proscenium wall to the support wall structure, whereas the stage system proposed in the application No. 59-120395 has no such mechanisms. On the other hand, a feature common to the two prior arts is that when the stage system is folded, rear portions of stage components associated with the respective guide posts are lifted along the heights of the guide posts while the proscenium wall is moved toward the support wall structure, maintaining an upright position thereof. After use either prior stage system may be compactly folded, or stored, to the vertical position immediately before the support wall structure and, hence, the greater part of the space occupied by the stage system may be freely used. When the stage system is unfolded, the tops of the stage components are lowered while the entire stage components are moved to horizontal positions and the proscenium wall is moved forward. Either prior stage system is not merely such a flexible system, but also provides a massive and stable stage comparable to a usual fixed-type stage originally constructed in a building.
After proposing the prior stage systems, the inventor reexamined them to see if they do not have any disadvantages which may be eliminated. As a result, the inventor has found that the mechanism for operating the stage components and the proscenium wall may be made more compact and more efficient. In addition, in the stage system proposed in the application No. 60-298461, since the proscenium wall is moved by rotating wheels provided in conjunction with the bottom of the proscenium wall by motors, the upper portion thereof may quake while the proscenium wall is being moved. The side link mechanisms which connect the proscenium wall to the support wall structure is not sufficient to prevent it. Thus the proscenium wall may not be moved stably.